JP7126878B2 - wiring board - Google Patents

Description

The present invention relates to wiring boards.

A wiring board used for a wearable terminal or the like may be used in a bent state. If the wiring board is used in a bent state, the wiring pattern and via wiring arranged in the bent portion may peel off due to the stress caused by the bending, resulting in defective conduction. Therefore, for example, countermeasures such as adjusting the pitch and diameter of the via wiring at the bent portion have been included.

In addition, copper foil with partially removed portions (through holes) is arranged on the front and back surfaces of the wiring board, and the flexibility of the wiring board is improved by shifting the copper foil-removed portion on the front surface and the copper foil-removed portion on the back surface. Attempts were also made to increase Also, attempts have been made to increase the flexibility of the wiring board by arranging the mesh ground layer on the outer peripheral side of the bent portion.

JP-A-2000-114728 JP 2016-4875 A

However, along with the multilayering of wiring boards, there has been a demand for further improvement in flexibility.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wiring board with improved flexibility.

The wiring board has a plurality of wiring layers and a solder resist layer arranged as an outermost layer, and is a wiring board having a longitudinal direction as a bending direction, and includes a component mounting section on which electronic components can be mounted, and an electronic component. and a component non-mounting portion that is not mountable, wherein the solder resist layer is not provided in the component non-mounting portion but is provided in the component non-mounting portion and is one wiring layer located in the component non-mounting portion. a plurality of elongated first through-holes are arranged at predetermined intervals with their longitudinal direction directed in a direction perpendicular to the bending direction ; Other wiring layers are arranged at predetermined intervals with the longitudinal direction oriented in a direction perpendicular to the bending direction, and the first through holes and the second through holes are arranged in a zigzag pattern in plan view, Said 2nd through-hole makes it a requirement that it partially overlaps with at least 4 said 1st through-holes in planar view .

According to the disclosed technique, it is possible to provide a wiring board with improved flexibility.

1 is a diagram illustrating a wiring board according to a first embodiment; FIG. 4 is a diagram illustrating the vicinity of an R portion in the wiring board according to the first embodiment; FIG. FIG. 4 is a diagram (part 1) illustrating a manufacturing process of the wiring board according to the first embodiment; FIG. 10 is a diagram (part 2) illustrating the manufacturing process of the wiring board according to the first embodiment; FIG. 10 is a diagram illustrating the vicinity of an R portion in a wiring board according to Modification 1 of the first embodiment; It is a figure explaining the conditions of simulation. It is a figure explaining the result of a simulation.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In addition, in each drawing, the same code|symbol may be attached|subjected to the same component part, and the overlapping description may be abbreviate|omitted.

<First Embodiment>
[Structure of Wiring Board According to First Embodiment]
First, the structure of the wiring board according to the first embodiment will be described. 1A and 1B are diagrams illustrating the wiring substrate according to the first embodiment, FIG. 1A being a plan view, and FIG. 1B being a cross-sectional view taken along line AA in FIG. is. FIGS. 2A and 2B are diagrams illustrating the vicinity of the R portion in the wiring board according to the first embodiment, FIG. 2A being a partially enlarged sectional view and FIG. 2B being a partially enlarged plan view. Note that FIG. 2(a) shows a cross section along line BB in FIG. 2(b). 2(b) shows only the insulating layer 18 and the wiring layer 19 in the R portion of FIG. 2(a).

1 and 2, the wiring board 1 is a flexible coreless multilayer wiring board. Here, flexibility refers to the property of being able to bend or bend.

As shown in FIG. 2, the wiring board 1 has a plurality of wiring layers (for example, 6 layers), and each wiring layer is laminated with an insulating layer interposed therebetween.

More specifically, the wiring board 1 includes a wiring layer 11, an insulating layer 12, a wiring layer 13, an insulating layer 14, a wiring layer 15, an insulating layer 16, a wiring layer 17, an insulating layer 18, and wiring. It has a structure in which a layer 19, an insulating layer 20, a wiring layer 21, and a solder resist layer 22 are sequentially laminated. However, the number of lamination of the wiring layer and the insulating layer can be appropriately determined according to need.

In the present embodiment, for convenience, the solder resist layer 22 side of the wiring board 1 is referred to as the upper side or one side, and the wiring layer 11 side is referred to as the lower side or the other side. Also, the surface of each portion on the solder resist layer 22 side is defined as one surface or upper surface, and the surface on the wiring layer 11 side is defined as the other surface or lower surface. However, the wiring board 1 can be used upside down, or can be arranged at an arbitrary angle. Planar view refers to viewing the object from the direction normal to one surface of the wiring board 1 (upper surface of the solder resist layer 22), and planar shape refers to viewing the object from one surface of the wiring substrate 1 (the upper surface of the solder resist layer 22). The top surface of the solder resist layer 22) is defined as the shape viewed from the normal direction.

Moreover, parallel and perpendicular in the present embodiment include not only strictly parallel and perpendicular but also generally parallel and perpendicular within the range in which the effects of the present embodiment are exhibited.

The wiring layer 11 is formed on the bottom layer of the wiring board 1 . The wiring layer 11 includes, for example, a gold (Au) film, a palladium (Pd) film, a nickel (Ni) film, and a copper (Cu) film, which are sequentially arranged in this order so that the gold (Au) film faces downward. It can be a laminated structure. However, in the wiring layer 11, the palladium (Pd) film and the nickel (Ni) film may not be formed.

The lower surface of the wiring layer 11 (the lower surface of the gold (Au) film in the above case) is exposed from the lower surface of the insulating layer 12 , and the upper surface (excluding the connection portion with the wiring layer 13 ) and side surfaces are covered with the insulating layer 12 . It is The lower surface of the wiring layer 11 can be flush with the lower surface of the insulating layer 12, for example. The thickness of the wiring layer 11 (total thickness of each film forming the wiring layer 11) can be, for example, approximately 10 to 20 μm. The wiring layer 11 can be used, for example, as pads connected to terminals of electronic components.

The insulating layer 12 is formed to cover the wiring layer 11 . As the material of the insulating layer 12, for example, an insulating resin (for example, thermosetting) having a low Young's modulus and flexibility can be used. Insulating resins having a low Young's modulus and flexibility include, for example, insulating resins containing polyimide-based resins, epoxy-based resins, or the like as main components. The thickness of the insulating layer 12 can be, for example, approximately 20 to 45 μm. The insulating layer 12 may contain a filler such as silica (SiO ₂ ).

The wiring layer 13 is formed on one side of the insulating layer 12 and electrically connected to the wiring layer 11 . The wiring layer 13 includes a via wiring filled in a via hole 12x penetrating the insulating layer 12 and exposing one surface of the wiring layer 11, and a wiring pattern formed on one surface of the insulating layer 12. ing. The via hole 12 x is an inverted truncated cone-shaped recess in which the diameter of the opening facing the insulating layer 14 is larger than the diameter of the bottom surface of the opening formed by the upper surface of the wiring layer 11 . The diameter of the opening of the via hole 12x can be, for example, approximately 60 to 70 μm.

As a material of the wiring layer 13, for example, copper (Cu) or the like can be used. The thickness of the wiring pattern forming the wiring layer 13 can be, for example, about 10 to 20 μm. The wiring layer 13 can be a fine wiring having a line and space (hereinafter abbreviated as line/space) of about 10 μm/10 μm to 20 μm/20 μm. In line/space, the line represents the wiring width, and the space represents the spacing between adjacent wirings (wiring spacing). For example, when the line/space is described as 10 μm/10 μm, it means that the wiring width is 10 μm and the interval between adjacent wirings is 10 μm.

The insulating layer 14 is formed on one surface of the insulating layer 12 so as to cover the wiring layer 13 . The material and thickness of the insulating layer 14 can be the same as those of the insulating layer 12, for example. The insulating layer 14 may contain a filler such as silica (SiO ₂ ).

The wiring layer 15 is formed on one side of the insulating layer 14 and electrically connected to the wiring layer 13 . The wiring layer 15 includes a via wiring filled in a via hole 14x penetrating the insulating layer 14 and exposing one surface of the wiring layer 13, and a wiring pattern formed on one surface of the insulating layer 14. ing. The via hole 14 x is an inverted truncated cone-shaped recess in which the diameter of the opening on the insulating layer 16 side is larger than the diameter of the bottom surface of the opening formed by the upper surface of the wiring layer 13 . The diameter of the opening of the via hole 14x can be, for example, approximately 60 to 70 μm. The material of the wiring layer 15 and the thickness and line/space of the wiring pattern forming the wiring layer 15 can be the same as those of the wiring layer 13, for example.

The insulating layer 16 is formed on one surface of the insulating layer 14 so as to cover the wiring layer 15 . The material and thickness of the insulating layer 16 can be the same as those of the insulating layer 12, for example. The insulating layer 16 may contain filler such as silica (SiO ₂ ).

The wiring layer 17 is formed on one side of the insulating layer 16 and electrically connected to the wiring layer 15 . The wiring layer 17 includes a via wiring filled in a via hole 16x penetrating the insulating layer 16 and exposing one surface of the wiring layer 15, and a wiring pattern formed on one surface of the insulating layer 16. ing. The via hole 16 x is an inverted truncated cone-shaped recess in which the diameter of the opening facing the insulating layer 18 is larger than the diameter of the bottom surface of the opening formed by the upper surface of the wiring layer 15 . The diameter of the opening of the via hole 16x can be, for example, approximately 60 to 70 μm. The material of the wiring layer 17 and the thickness and line/space of the wiring pattern forming the wiring layer 17 can be the same as those of the wiring layer 13, for example.

The insulating layer 18 is formed on one surface of the insulating layer 16 so as to cover the wiring layer 17 . The material and thickness of the insulating layer 18 can be the same as those of the insulating layer 12, for example. The insulating layer 18 may contain a filler such as silica (SiO ₂ ).

The wiring layer 19 is formed on one side of the insulating layer 18 and electrically connected to the wiring layer 17 . The wiring layer 19 includes a via wiring filled in a via hole 18x penetrating the insulating layer 18 and exposing one surface of the wiring layer 17, and a wiring pattern formed on one surface of the insulating layer 18. ing. The via hole 18 x is an inverted truncated cone-shaped recess in which the diameter of the opening facing the insulating layer 20 is larger than the diameter of the bottom surface of the opening formed by the upper surface of the wiring layer 17 . The diameter of the opening of the via hole 18x can be, for example, approximately 60 to 70 μm. The material of the wiring layer 19 and the thickness and line/space of the wiring pattern forming the wiring layer 19 can be the same as those of the wiring layer 13, for example.

The insulating layer 20 is formed on one surface of the insulating layer 18 so as to cover the wiring layer 19 . The material and thickness of the insulating layer 20 can be the same as those of the insulating layer 12, for example. The insulating layer 20 may contain filler such as silica (SiO ₂ ).

The wiring layer 21 is formed on one side of the insulating layer 20 and electrically connected to the wiring layer 19 . The wiring layer 21 includes a via wiring filled in a via hole 20x penetrating the insulating layer 20 and exposing one surface of the wiring layer 19, and a wiring pattern formed on one surface of the insulating layer 20. ing. The via hole 20 x is an inverted truncated cone-shaped recess in which the diameter of the opening on the solder resist layer 22 side is larger than the diameter of the bottom of the opening formed by the upper surface of the wiring layer 19 . The diameter of the opening of the via hole 20x can be, for example, approximately 60 to 70 μm. The material of the wiring layer 21 and the thickness and line/space of the wiring pattern forming the wiring layer 21 can be the same as those of the wiring layer 13, for example.

The solder resist layer 22 is formed on one surface of the insulating layer 20 so as to cover the wiring layer 21 . The solder resist layer 22 can be made of, for example, a photosensitive resin such as an epoxy resin or an acrylic resin. The thickness of the solder resist layer 22 can be, for example, approximately 15 to 35 μm.

The solder resist layer 22 has an opening 22x, and a part of the upper surface of the wiring layer 21 is exposed in the opening 22x. The planar shape of the opening 22x can be circular, for example. If necessary, a metal layer may be formed on the upper surface of the wiring layer 21 exposed in the opening 22x, or an anti-oxidation treatment such as an OSP (Organic Solderability Preservative) treatment may be performed. Examples of metal layers include an Au layer, a Ni/Au layer (a metal layer in which a Ni layer and an Au layer are laminated in this order), a Ni/Pd/Au layer (a Ni layer, a Pd layer, and an Au layer in this order). laminated metal layer) and the like.

The wiring layer 21 exposed in the opening 22x can be used as a pad to be connected to the terminal of the electronic component.

In the wiring board 1, since the upper surface of each wiring layer arranged on each via wiring is flat and no concave portion is formed, a stacked via structure in which the via wiring is vertically stacked as shown in FIG. 2(a) is realized. can do. As a result, the density of the wiring layers of the wiring board 1 can be improved, and the reliability of electrical connection between the wiring layers through the via wiring can be improved. However, a form without a stack via structure may also be used.

The wiring board 1 has a component mounting portion on which electronic components can be mounted and a component non-mounting portion R on which electronic components cannot be mounted. In the wiring board 1, the area other than the component non-mounting area R indicated by the dashed line is the component mounting area, and the electronic component can be mounted at an appropriate position of the component mounting area.

In the wiring board 1, the component non-mounting portion R is a bendable portion designed on the assumption that it will be bent in advance. In FIG. 1, two component non-mounting portions R are provided on the wiring board 1, but one component non-mounting portion R may be provided, or three or more component non-mounting portions R may be provided. Thus, by providing one or more non-mounting parts R, the wiring board 1 can be easily moved in the longitudinal direction (the direction of line AA in FIG. 1(a) or line BB in FIG. 2(b)). can be bent to That is, the wiring board 1 has the longitudinal direction as the bending direction.

The wiring patterns forming each wiring layer may be arranged in either the component-mounted portion or the non-component-mounted portion R, but the via wiring is arranged only in the component-mounted portion. By not arranging via wiring in the component non-mounting portion R, but by arranging the via wiring only in the component mounting portion that is not supposed to be bent, cracks occur in the via wiring when the component non-mounting portion R is bent. can be prevented.

A solid pattern 19G connected to GND is formed on the wiring layer 19 positioned in the component non-mounting portion R. As shown in FIG. A plurality of elongated through holes 19y are formed in the solid pattern 19G. The planar shape of the through-hole 19y is not particularly limited as long as it is an elongated shape having a longitudinal direction and a lateral direction. includes a shape formed in an arc).

Each through-hole 19y is arranged at predetermined intervals with its longitudinal direction oriented in a direction perpendicular to the bending direction of the wiring board 1. As shown in FIG. In FIG. 2B, the through holes 19y are arranged in two rows parallel to the bending direction of the wiring board 1, but they may be arranged in one row or in three or more rows.

The longitudinal length L1 of the through _- hole 19y can be, for example, approximately 400 to 700 μm. The length L2 of the through-hole _19y in the lateral direction can be, for example, approximately 100 to 400 μm. The interval G1 between the through holes 19y adjacent to each other in the direction perpendicular to the bending direction of the wiring board ₁ can be, for example, about 20 to 100 μm. The interval G2 between the through holes 19y adjacent to each other in the bending direction of the wiring board ₁ can be, for example, approximately 20 to 100 μm.

From the viewpoint of reducing the wiring pattern formation density in the component non-mounting portion R and ensuring good flexibility, the interval G2 between the through holes _19y adjacent to each other in the bending direction of the wiring board 1 is the width of the through holes 19y. It is preferably arranged to be less _than length L2. The same applies to through holes 13y, 15y, and 17y, which will be described later.

Solid patterns 13G, 15G, and 17G connected to GND are formed on the wiring layers 13, 15, and 17 positioned in the non-mounting portion R, similarly to the solid pattern 19G. Through-holes 13y, 15y, and 17y having the same size as the through-hole 19y are formed in the solid patterns 13G, 15G, and 17G at positions overlapping the respective through-holes 19y in plan view.

A solid pattern is also formed on the wiring layers 11 and 21 located in the component non-mounting portion R, and through holes having the same size as the through holes 19y are formed at positions overlapping the respective through holes 19y in a plan view. good too. However, from the viewpoint of reducing the wiring pattern formation density in the component non-mounting portion R and ensuring good flexibility, the component non-mounting portion R It is preferable that the number of wiring layers in is smaller. In the wiring board 1, the number of wiring layers in the component non-mounting portion R is four, but may be five or three or less.

In each wiring layer located in the component non-mounting portion R, the solid pattern connected to GND functions as a shield pattern for shielding noise. A wiring pattern other than the solid pattern may be formed.

For example, in an arbitrary wiring layer located in the component non-mounting portion R, both sides of the signal pattern may be shielded with a GND pattern. In this case, the through holes may be arranged to avoid the signal pattern, or may be formed in the signal pattern as long as the signal pattern is not disconnected. Further, for example, the wiring layers 13 and 19 located outside in the thickness direction are formed with only solid GND patterns, and the wiring layers 15 and 17 located inside in the thickness direction are formed with only signal patterns. good too.

[Method for Manufacturing Wiring Board According to First Embodiment]
Next, a method for manufacturing the wiring board according to the first embodiment will be described. 3 and 4 are diagrams illustrating the manufacturing process of the wiring board according to the first embodiment. In this embodiment mode, an example of a step of manufacturing wiring boards one by one over a support and removing the support is shown. It is good also as a process which separates and makes each wiring board.

First, in the process shown in FIG. 3A, a support 300 having a flat upper surface is prepared, and a resist layer 400 (for example, a , dry film resist, etc.). A metal plate, a metal foil, or the like can be used as the support 300. In this embodiment, an example of using a copper foil as the support 300 is shown. The thickness of the support 300 can be, for example, approximately 18 to 100 μm.

Next, in the step shown in FIG. 3B, for example, a wiring layer is formed on the upper surface of the support 300 exposed in the opening 400x of the resist layer 400 by electroplating or the like using the support 300 as a plating power supply layer. 11 is formed. After that, the resist layer is removed. The material and thickness of the wiring layer 11 are as described above.

Next, in the step shown in FIG. 3C, for example, a semi-cured film resin is laminated on the upper surface of the support 300 so as to cover the upper surface and side surfaces of the wiring layer 11, and is cured to form an insulating layer. form 12; Alternatively, instead of laminating a film-like resin, the insulating layer 12 may be formed by applying a liquid or paste-like resin and then curing it. The material and thickness of the insulating layer 12 are as described above.

Next, in the step shown in FIG. 3D, a via hole 12x is formed in the insulating layer 12 to penetrate the insulating layer 12 and expose the upper surface of the wiring layer 11. Next, in the step shown in FIG. The via hole 12x can be formed, for example, by a laser processing method using a CO ₂ laser or the like. After forming the via hole 12x, it is preferable to perform a desmear treatment to remove resin residue adhering to the surface of the wiring layer 11 exposed at the bottom of the via hole 12x.

Next, in the step shown in FIG. 4A, the wiring layer 13 is formed on one side of the insulating layer 12. Next, in the step shown in FIG. The wiring layer 13 includes via wirings filled in the via holes 12 x and wiring patterns formed on the upper surface of the insulating layer 12 . A solid pattern 13G connected to GND is formed in the component non-mounting portion R, and a through hole 13y is formed in the solid pattern 13G. The via wiring, the wiring pattern, and the solid pattern 13G having the through holes 13y, which constitute the wiring layer 13, can be simultaneously formed using, for example, a semi-additive method or a subtractive method. The material of the wiring layer 13, the thickness of the wiring pattern forming the wiring layer 13, and the line-and-space are as described above. Wiring layer 13 is electrically connected to wiring layer 11 exposed at the bottom of via hole 12x.

Next, in the process shown in FIG. 4B, the same processes as those shown in FIGS. An insulating layer 18, a wiring layer 19, an insulating layer 20, and a wiring layer 21 are sequentially formed.

Next, in the step shown in FIG. 4C, a solder resist layer 22 is formed on the upper surface of the insulating layer 20 so as to cover the wiring layer 21 . The solder resist layer 22 is formed by, for example, applying a liquid or paste photosensitive epoxy resin or acrylic resin to the upper surface of the insulating layer 20 so as to cover the wiring layer 21 by a screen printing method, a roll coating method, or a spin coating method. It can be formed by coating by a coating method or the like. Alternatively, for example, a film-like photosensitive epoxy resin or acrylic resin may be laminated on the upper surface of the insulating layer 20 so as to cover the wiring layer 21 .

Next, by exposing and developing the solder resist layer 22, an opening 22x exposing a part of the upper surface of the wiring layer 21 is formed in the solder resist layer 22 (photolithography method). The opening 22x may be formed by laser processing or blasting. In that case, it is not necessary to use a photosensitive material for the solder resist layer 22 . The planar shape of the opening 22x can be circular, for example. The diameter of the opening 22x can be arbitrarily designed according to the object to be connected (semiconductor chip, etc.).

The metal layer described above may be formed on the upper surface of the wiring layer 21 exposed at the bottom of the opening 22x, for example, by electroless plating. Also, instead of forming the metal layer, an anti-oxidation treatment such as an OSP treatment may be performed. Also, an external connection terminal such as a solder bump may be formed on the upper surface of the wiring layer 21 exposed at the bottom of the opening 22x.

After the step shown in FIG. 4(c), the wiring substrate 1 (see FIGS. 1 and 2) is completed by removing the support 300 shown in FIG. 4(c). The support 300, which is a copper foil, can be removed by wet etching using, for example, an aqueous solution of ferric chloride, an aqueous solution of cupric chloride, an aqueous solution of ammonium persulfate, or the like. The step of forming the solder resist layer 22 shown in FIG. 4C may be performed after the support 300 is removed.

In this manner, the wiring board 1 has a non-mounted component portion R defined therein, and the wiring layer positioned in the non-mounted component portion R has a plurality of elongated through holes extending in the bending direction of the wiring board 1 in the longitudinal direction. are arranged at predetermined intervals in a direction perpendicular to the As a result, the flexural modulus of the component non-mounting portion R can be reduced, and the bendability of the component non-mounting portion R can be improved.

Further, each through-hole provided in the component non-mounting portion R can function as a degas hole. Since each through-hole functions as a degas hole, the risk of voids occurring inside the wiring substrate 1 can be reduced. Here, the degas hole is a hole for venting gas generated inside the wiring board during heating in the manufacturing process of the wiring board to escape to the outside.

In the wiring board 1, the component non-mounting portion R may be composed only of a flexible insulating layer without providing a solder resist layer. In the wiring board 1, the component non-mounting portion R may be formed so that the wiring and pads are not exposed from the outermost layer.

<Modification 1 of the first embodiment>
Modification 1 of the first embodiment shows an example in which the arrangement of through holes provided in wiring layers adjacent in the thickness direction in the non-mounted part R is different. In addition, in the modification 1 of the first embodiment, the description of the same components as those of the already described embodiment may be omitted.

5A and 5B are diagrams illustrating the vicinity of the R portion in the wiring board according to Modification 1 of the first embodiment, FIG. 5A being a partially enlarged cross-sectional view corresponding to FIG. (b) is a partially enlarged plan view corresponding to FIG. 2(b). Note that FIG. 5(a) shows a cross section along line CC of FIG. 5(b). 5(b) shows only the wiring layer 17, the insulating layer 18, and the wiring layer 19 of the R portion of FIG. 5(a).

Referring to FIG. 5, in the wiring board 1A, the through holes provided in the wiring layers adjacent in the thickness direction in the component non-mounting portion R are arranged in a zigzag pattern in plan view.

That is, a solid pattern 19G connected to GND is formed on the wiring layer 19 located in the non-mounting portion R of the component. In the solid pattern 19G, similarly to the wiring board 1, a plurality of elongated through holes 19y are formed with the longitudinal direction perpendicular to the bending direction of the wiring board 1A (the direction of line CC in FIG. 5B). are arranged at predetermined intervals.

A solid pattern 17G connected to GND is formed in the wiring layer 17 located in the component non-mounting portion R, similarly to the solid pattern 19G. In the solid pattern 17G, through-holes 17z having the same size as the through-holes 19y are formed so as to be arranged in a staggered manner with the through-holes 19y in plan view and partially overlap with the through-holes 19y. It is

A solid pattern 15G connected to GND is formed in the wiring layer 15 located in the component non-mounting portion R, similarly to the solid pattern 19G. Through-holes 15y having the same size as the through-holes 19y are formed in the solid pattern 15G at positions overlapping the respective through-holes 19y in plan view.

A solid pattern 13G connected to GND is formed in the wiring layer 13 positioned in the component non-mounting portion R, similarly to the solid pattern 19G. In the solid pattern 13G, through-holes 13z (not shown in FIG. 5) having the same size as the through-holes 17z are formed at positions overlapping the through-holes 17z in plan view.

In this way, the wiring board 1A has the component non-mounting portion R defined therein, and the wiring layer positioned in the component non-mounting portion R has a plurality of elongated through holes extending in the bending direction of the wiring board 1A in the longitudinal direction. are arranged at predetermined intervals in a direction perpendicular to the In the wiring board 1A, the through holes provided in the wiring layers adjacent in the thickness direction in the component non-mounting portion R are arranged in a staggered manner in plan view, and the through holes formed in the wiring layers adjacent in the thickness direction are arranged in a zigzag pattern. The pores partially overlap each other.

As a result, it is possible to ensure the same good flexibility as that of the wiring board 1 in the non-mounting part R, and to improve the function of each through-hole as a degassing hole. Since the through-holes partially overlap each other, the gas can easily escape). By improving the function of each through-hole as a degas hole, the wiring board 1A can further reduce the risk of voids occurring inside the wiring board 1A compared to the wiring board 1. FIG.

<simulation>
6(a) to 6(e) show a wiring board having a layer structure similar to that of the wiring board 1 (the total number of wiring layers is 6, and the number of wiring layers in the part non-mounting portion R is 4). A simulation was performed for the flexural modulus in each case. Simulations were performed using Ansys Workbench v18 with a 1/2 symmetric model.

FIG. 6A shows a case where no through holes are formed in each wiring layer 100 located in the non-mounting portion R of the wiring board (only a solid pattern without through holes is formed). Here, each wiring layer 100 means the inner four wiring layers corresponding to the wiring layers 13, 15, 17 and 19 of the wiring board 1 (FIGS. 6B to 6). The same applies to (e)). Also, the arrow indicates the bending direction of the wiring board (the longitudinal direction of the wiring board) (the same applies to FIGS. 6B to 6E).

FIG. 6B shows a case where through-holes 110 having a circular planar shape are formed in a matrix in each wiring layer 100 located in the component non-mounting portion R of the wiring board. In each wiring layer 100 positioned in the component non-mounting portion R, a through hole having the same size as the through hole 110 is formed at a position overlapping the through hole 110 in plan view. The diameter of the through-holes 110 is φ250 μm, and the pitch of the through-holes 110 in the row and column directions is 300 μm.

FIG. 6(c) shows a case where through-holes 120 having a circular planar shape are formed in a matrix in each wiring layer 100 located in the component non-mounting portion R of the wiring board. A through-hole having the same size as the through-hole 120 is formed in each wiring layer 100 located in the component non-mounting portion R. As shown in FIG. However, the through-holes provided in the wiring layers adjacent in the thickness direction in the non-mounting part R are arranged in a zigzag pattern in plan view. The diameter of the through-holes 120 is φ250 μm, and the pitch of the through-holes 120 in the row and column directions is 300 μm.

FIG. 6(d) shows through-holes 130 having an elongated planar shape (a shape in which the short sides of a rectangle are formed in an arc shape) arranged in a matrix in each wiring layer 100 located in the component non-mounting portion R of the wiring board. This is the case when it is formed. That is, the through-holes 130 having an elongated planar shape are arranged at predetermined intervals with the longitudinal direction parallel to the bending direction of the wiring board.

A through-hole having the same size as the through-hole 130 is formed in each wiring layer located in the component non-mounting portion R. As shown in FIG. However, the through-holes provided in the wiring layers adjacent in the thickness direction in the non-mounting part R are arranged in a zigzag pattern in plan view. The rectangular portion of through-hole 130 (the portion excluding arc-shaped portions at both ends) has a width of 250 μm and a length of 300 μm. Also, the arcuate portions at both ends of the through-hole 130 are half circles (semicircles) with a diameter of 250 μm. The pitch of the through-holes 130 in the row direction is 600 μm, and the pitch in the column direction is 300 μm.

FIG. 6E shows through-holes 140 each having an elongated planar shape (a shape in which the short sides of a rectangle are formed in an arc shape) arranged in a matrix in each wiring layer 100 positioned in the non-mounting portion R of the wiring board. This is the case when it is formed. That is, the through-holes 140 having an elongated planar shape are arranged at predetermined intervals with their longitudinal direction directed in a direction perpendicular to the bending direction of the wiring substrate.

A through-hole having the same size as the through-hole 140 is formed in each wiring layer located in the non-mounting portion R of the component. However, the through-holes provided in the wiring layers adjacent in the thickness direction in the non-mounting part R are arranged in a zigzag pattern in plan view. The rectangular portion of through-hole 140 (the portion excluding arc-shaped portions at both ends) has a width of 250 μm and a length of 300 μm. Also, the arcuate portions at both ends of the through-hole 140 are half circles (semicircles) with a diameter of φ250 μm. The pitch of the through-holes 140 in the row direction is 300 μm, and the pitch in the column direction is 600 μm.

When a simulation was performed on the flexural modulus in each case shown in FIGS. 6(a) to 6(e), the results shown in FIG. 7 were obtained.

From FIG. 7 , compared with the case of not forming the through hole of FIG. 6A, the case of forming the circular through hole of FIGS. It can be seen that the flexural modulus of the component non-mounting portion R is reduced when the elongated through-holes of (e) are formed.

6D and 6E are more effective than the circular through holes shown in FIGS. 6B and 6C. It can be seen that the flexural modulus of the component non-mounting portion R is greatly reduced. In particular, when the elongated through-holes are arranged with the longitudinal direction perpendicular to the bending direction of the wiring board as shown in FIG. The bending elastic modulus of the component non-mounting portion R is further reduced by about 15% as compared to the case of arranging them in the parallel direction.

Thus, by forming through holes in each wiring layer positioned in the component non-mounting portion R, the bending elastic modulus of the component non-mounting portion R can be reduced. Among others, it was confirmed that the bending elastic modulus of the non-mounted part R can be reduced most when the elongated through-holes are arranged with the longitudinal direction perpendicular to the bending direction of the wiring board. That is, from the viewpoint of ensuring good bendability in the component non-mounting portion R, the form of FIG. 6(e) can be said to be the most preferable.

According to the simulation results of FIGS. 6(b) and 6(c), whether or not the through-holes are arranged in a zigzag pattern in plan view has a large effect on the bending elastic modulus of the component non-mounting portion R. no. Therefore, even if the through-holes 140 are not arranged in a staggered manner in plan view in FIG.

Although the preferred embodiments and the like have been described in detail above, the present invention is not limited to the above-described embodiments and the like, and various modifications can be made to the above-described embodiments and the like without departing from the scope of the claims. Modifications and substitutions can be made.

1, 1A wiring board 11, 13, 15, 17, 19, 21 wiring layer 12, 14, 16, 18, 20 insulating layer 12x, 14x, 16x, 18x, 20x via hole 13G, 15G, 17G, 19G solid pattern 13y, 13z, 15y, 17y, 17z, 19y through hole 22 solder resist layer 22x opening R non-mounting part

Claims (6)

A wiring board having a plurality of wiring layers and a solder resist layer arranged as an outermost layer, and having a longitudinal direction as a bending direction,
a component mounting section capable of mounting electronic components;
and a component non-mounting part on which electronic components cannot be mounted,
The solder resist layer is not provided in the component non-mounting portion but is provided in the component mounting portion,
A plurality of elongated first through holes are arranged at predetermined intervals in one wiring layer positioned in the component non-mounting portion, with the longitudinal direction directed in a direction perpendicular to the bending direction ,
Another wiring layer located in the component non-mounting portion and having a plurality of elongated second through holes arranged at predetermined intervals with the longitudinal direction thereof directed in a direction perpendicular to the bending direction,
the first through-holes and the second through-holes are arranged in a zigzag pattern in plan view,
The wiring board , wherein the second through holes partially overlap with at least four of the first through holes in plan view . 2. The plurality of second through-holes according to claim 1 , wherein the plurality of second through-holes are arranged such that the interval between the second through-holes adjacent to each other in the bending direction is smaller than the length of the second through-holes in the lateral direction. wiring board. 3. The plurality of first through-holes are arranged such that the interval between the first through-holes adjacent to each other in the bending direction is smaller than the length of the first through-holes in the transverse direction. The wiring board according to . having a via wiring that electrically connects vertically adjacent wiring layers with an insulating layer interposed therebetween;
4. The wiring board according to claim 1 , wherein the via wiring is arranged only in the component mounting portion. The wiring board according to any one of claims 1 to 4 , wherein the number of wiring layers in the component non-mounting portion is smaller than the number of wiring layers in the component mounting portion. 6. The wiring board according to any one of claims 1 to 5 , wherein at least one wiring layer located in the component non-mounting portion is a solid pattern connected to GND.

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